1. Field of the Invention
Example embodiments relate to communication systems, for example, methods of jointly assigning resources in multi-hop wireless communication systems.
2. Description of the Related Art
Orthogonal Frequency Division Multiple Access (OFDMA) has been adopted as the multiple access technique for many wireless communication systems, including systems that operate according to the Institute of Electrical and Electronics Engineers (IEEE) 802.16e standard (also known as WiMAX), Universal Mobile Telecommunications System-Long Term Evolution (UMTS-LTE), which is currently being standardized by the Third Generation Partnership Project (3GPP), and High Rate Packet Data Revision C, which is currently being standardized by the Third Generation Partnership Project 2 (3GPP2).
In a conventional OFDMA system, available bandwidth is divided into a plurality of subcarrier frequencies (commonly referred to as bands, tones, or subcarriers, and used interchangeably as such herein) and time is segmented into symbols. One or more subcarriers, adjacent or distributed over the frequency band, may be grouped into subchannels. Moreover, one or more symbols may be grouped into time slots, and the time slots may be grouped into frames. Typically, a base station is responsible for assigning resource units across time and frequency for all single-hop communication links between the base station and subscriber stations, between base stations and relay stations or between base stations and base stations. A single-hop refers to a direct communication link between two network nodes without an intermediate node helping the communication, whereas multi-hop refers to communication between two network nodes in which the transmitted data is routed through intermediate nodes. Such links may be unidirectional or bi-directional in nature. To achieve higher system throughputs, resources may be assigned based on channel quality information, which may vary across time, frequency and/or space. Better channel quality typically yields higher throughputs.
In a conventional wireless communications network, base stations assign resources locally. That is, for example, base stations assign resources only for links that originate or terminate at the base station. Resource assignment decisions are based on channel quality information on these local links. Further, resource decisions spanning power, tone allocation, scheduling and routing are conventionally performed independently to reduce complexity (e.g., layering). Doing so, however, may significantly reduce system performance.